Comet ISON: Is Potential 'Comet of the Century' Already Fizzling Out?

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It doesn't look like Comet ISON will live up to the considerable
hype, one researcher says.

ISON has been billed as a potential " comet
of the century," with some experts saying it could blaze as
brightly as the full moon around the time of its close solar
approach in late November. But the comet's recent behavior
suggests that such a dazzling show is not in the cards, says
astronomer Ignacio Ferrín of the University of Antioquia in
Medellín, Colombia.

"Comet ISON has presented a peculiar behavior," Ferrín said in a
statement Monday (July 29). "The light curve has exhibited a
'slowdown event' characterized by a constant brightness, with no
indication of a brightness increase tendency. This slowdown took
place around January 13th, 2013. For 132 days after that date and
up to the last available observation, the brightness has remained
constant." [ Photos
of Comet ISON: A Potentially Great Comet ]

Comet ISON's recent performance has a precedent that's not
terribly encouraging. In 2003, Comet C/2002 O4 Hönig exhibited a
brightness plateau for 52 days and then disintegrated, Ferrín
noted.

Comet ISON is slated to skim just 724,000 miles (1.16 million
kilometers) above the surface of the sun on Nov. 28. Thus far,
most scientists have been hedging their bets about the icy
wanderer's performance. It's difficult to predict how any
comet will behave during a close solar passage, they say, and
especially tough to do so for "dynamically new" comets like ISON
that are making their first trip to the inner solar system from
the frigid, distant Oort Cloud.

The forecast could start firming up a bit soon, however. Comet
ISON — whose nucleus is thought to be just 3 to 4 miles (4.8 to
6.5 km) wide — is slated to cross the "frost line" within the
next few weeks, scientists say.

This boundary, which lies about 230 to 280 million miles (370 to
450 million km) from the sun, marks the point at which ISON's
water ice will start boiling off into space. (Until now, most of
its activity has been driven by sublimating carbon dioxide.)

ISON should brighten as it crosses the frost line, and scientists
and skywatchers should get a better idea of how tough the comet
is, researchers say. Some inbound comets haven't survived their
trip past the frost line.

Comet ISON was discovered last September by amateur astronomers
Vitali Nevski and Artyom Novichonok. It takes its name from the
equipment the duo used — the International Scientific Optical
Network (ISON) near Kislovodsk, Russia.

Skywatchers aren't the only people eagerly tracking ISON's
journey toward the sun. NASA has organized a coordinated
observation campaign enlisting many instruments on the ground and
in space. The goal is to learn more about Comet ISON's
composition, which could in turn reveal insights about the early
days of the solar system.

UPDATE: Scientists will be meeting Thursday (Aug. 1) and Friday
(Aug. 2) to form a game plan for observing and studying comet
ISON during a workshop at the Johns Hopkins University Applied
Physics Laboratory (APL) in Laurel, Md. The workshop will be
webcast from 9 a.m. EDT to 5 p.m. EDT both days. You
can watch
live here on SPACE.com, directly at the workshop
homepage, or at LiveStream.

Editor's note: If you snap a photo of Comet
ISON or any other amazing night sky object and you'd like to
share it for a possible story or image gallery, please send
images, comments and details to managing editor Tariq Malik
at spacephotos@space.com.